Firing mechanism for firearm

ABSTRACT

A firing mechanism is provided which fires the firearm automatically as the breech block closes. The mechanism includes a hammer-engaging sear which is provided with a cam laterally offset from the sear, the cam being positioned above the operating arm for closing the breech block. As the operating arm is pivoted to close the breech block, it engages the cam and moves the sear to release the hammer.

waited States Patent [191 Kotas et al.

[ Oct. 9, 1973 FIRING MECHANISM FOR FIREARM Inventors: John A. Kotas,Chicago Heights;

James V. Slattery, Oak Forest, both of Ill.

Filed: June 30, 1972 App]. No.: 267,963

US. Cl. 89/24, 89/27 R Int. Cl F4lf 11/02, F41f 13/04 Field of Search42/14, 23, 24, 69 R;

References Cited UNITED STATES PATENTS Diaz 42/24 PrimaryExaminer-Stephen C. Bentley Attorney-John W. Chestnut et al.

[5 7] ABSTRACT A firing mechanism is provided which fires the firearmautomatically as the breech block closes. The mechanism includes ahammer-engaging sear which is provided with a cam laterally offset fromthe sear, the cam being positioned above the operating arm for closingthe breech block. As the operating arm is pivoted to close the breechblock, it engages the cam and moves the sear to release the hammer.

9 Claims, 9 Drawing Figures PATENTED 91915 3.763.742

SHEET 10F 3 FIGJ v ,0

START 26 '7 sum 2 OF '3' PIC-3.3

F'IGA PATENTEU 91975 SHEET 3 BF 3 FIG.7

FIRING MECHANISM FOR FIREARM BACKGROUND This invention relates to afiring mechanism for firearms, and, more particularly, to a firingmechanism for firearms which include a breech block which is movable byan operating arm between unfired and fired posltions.

The invention finds particular utility in kiln guns such as described inco-owned U.S. Pat. Nos. 2,415,952 and 2,977,855 and will be described inconjunction therewith. As described in these patents, kiln gunsconventionally include a vertically movable breech block which ismovable between an open position in which a shell can be inserted into ashell chamber in the barrel and a fired or closed position in which thefiring pin carried by the breech block is in position to strike theshell. The firing pin is actuated by a hammer, and the hammer is held inthe ready to fire position by a scar. Heretofore, the sear has generallybeen disengaged from the hammer after the breech block is closed bypulling a lanyard connected to the sear or by a trigger. Firearmsconstructed in this manner require a two-step procedure to fire the gunafter the shell is loaded. The breech block must first be closed, andthen the sear must be released by pulling the lanyard or the trigger.

U.S. Pat. No. 2,977,855 discloses a means for releasing the sear as thebreech block is closed, but this searreleasing means is not entirelysatisfactory. A screw abutment for engaging the sear is carried by thebreech block, and the adjustment of this screw abutment is rathercritical since the screw must be positioned to release the sear exactlyas the breech block reaches its fully closed position. If the sear wasreleased prematurely, the shot misfired, and unless the adjustment wassuch that the releasing movement of the sear was initiated prior to thetime the breech block stopped in its closed position, the sear might notrelease at all. Fur-' ther, even if the adjustment is proper, therelatively small contacting area between the screw and the sear issubject to wear, and the parts may lose their original setting.

SUMMARY The invention provides an automatic firing mechanism thatreleases the sear in timed relation to the closing of the breech blockand which does not require adjustment once the initial timedrelationship is set. The scar is provided with a cam which is directlyengageable with the operating arm for the breech block, and the cam andthe operating arm are engageable over substantially the entire width ofthe arm. Both the cam and the operating arm are formed of hardenedsteel, and the hard surfaces and the substantial extent of the engagingsurfaces minimize wear of these parts. Since the parts are notadjustable, they are tamperproof and are not subject to human error. Thecam is formed integrally with the sear, and the number of parts requiredfor conventional guns is reduced. The automatic firing of the gunincreases the speed of operation and reduces operating costs.

DESCRIPTION OF THE DRAWING The invention will be explained inconjunction with an illustrative embodiment shown in the accompanyingdrawing, in which:

FIG. 1 is a fragmentary side elevational view partially broken away, ofa kiln gun equipped with the invention, the gun being shown in the readyto fire position;

FIG. 2 is a view similar to FIG. 1 showing the gun in the firedposition;

FIG. 3 is an enlarged fragmentary sectional view taken along line 33 ofFIG. 1;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is an enlarged perspective view of the camequipped sear;

FIG. 6 is another perspective view of the sear;

FIG. 7 is a side elevational view of the sear;

FIG. 8 is an end elevational view of the sear; and

FIG. 9 is a fragmentary plan view of the camming surface of the sear.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to FIGS. 1 and 2, thenumeral 10 designates a kiln gun generally of the type described in U.S.Pat. Nos. 2,415,952 and 2,977,855, to which reference may be had fordetails. The gun includes a frame or carriage 11 upon which are mounteda barrel l2 and a yoke 13. The barrel is threadedly secured to the yokeby barrel nut 14 and terminates adjacent a vertically extending breechblock passage 15 (FIG. 3) provided through the yoke. A shell receivingchamber 16 in the barrel communicates with the breech passage Anelongated vertically extending breech block 17 is slidably received bythe breech block passage and carries a spring-retractable firing 18which is mounted for horizontal sliding movement and a hammer 19 whichis mounted for pivotal movement in a vertical plane. The hammer ismounted within a recess 20 in the rear of the breech block by a pin 21and is urged to rotate toward the firing pin by a plunger 22 and spring23 carried by the breech block.

The breech block can be moved vertically within the breech passage bymeans of an elongated operating arm 24 which is connected to shaft 25for pivoting in a vertical plane. The shaft is rotatably mounted in theframe 11 and is rotatable by lever arm 26 which is connected thereto.The operating arm is provided with an elongated slot 27 which slidablyreceives a rotary stud shaft 28 extending transversely from the breechblock, and as the operating arm is rotated by the lever arm, the breechblock is caused to slide vertically within the yoke.

The upper end of the breech block is provided with a shell loading andejecting channel 30 (FIG. 4) which will expose the shell-receivingchamber 16 of the barrel when the breech block is lowered to its loadingposition by rotating the lever arm clockwise to the position indicatedin phantom in FIG. 1 at 26'. When the breech block is raised to itsfired position illustrated in FIG. 2 by rotating the lever arm forwardlyor counterclockwise, the firing pin 18 will be generally horizontallyaligned with the shell casing.

A sear 31 is pivotally mounted within a recess 32 (FIGS. 3 and 4) in theyoke 13 by pivot pin 33, and the sear is urged to pivot forwardly, orclockwise as viewed in FIGS. 1 and 2, by a spring 34. One end of thespring is received in an opening 35 (FIGS. 6 and 8) in the rear of thesear, and the other end abuts the yoke.

The sear is shown in detail in FIGS. 5-9. The sear includes planarvertically extending side surfaces 36 and 37, a curved front surface 38,and a rear surface 39. The upper portion of the sear extends forwardlyto provide a hammer-engaging tooth 40, and the lower portion of the searextends rearwardly to provide a stop foot 41 which is engageable withthe yoke to prevent excessive forward rotation of the sear. A cam 42extends laterally outwardly from the side surface 36 and includes a flatcamming bottom surface 43, a Hat front surface 44 which extendsgenerally perpendicularly to the surface 43, and a curved upper surface45. The sear and cam are preferably formed integrally, as by casting,and a bore 46 extends through the cam and the sear for rotatablyreceiving the pivot pin 33.

Referring now to FIG. 4, the operating arm 24 extends alongside thebreech block offset from a vertical center plane through the hammer,scar, and breech block and within a recessed or cutaway portion in thebottom of the breech block. The width of the operating arm and the widthof the recess in the breech block are seen to be substantially the same,and the right side of the arm as viewed in FIG. 4 is substantiallyaligned with the right side of the upper non-recessed part of the breechblock. The cam 42 extends laterally from the sear above the uppersurface of the operating arm to such an extent that substantially thefull width of the arm is engageable with the cam.

The gun is loaded by moving the lever arm 26 to the position shown inphantom at 26 in FIG. 1. This rearward movement of the lever arm rotatesthe operating arm 24 clockwise about the pivot provided by the shaft 25and lowers the breech block to expose the cartridgereceiving chamber ofthe barrel. After the shell is inserted, the lever arm 26 is pushedforwardly to raise the breech block. When the tooth 47 of the hammer 19engages the tooth 40 of the sear, further upward movement of the breechblock will cause the hammer to pivot about its mounting pin 21 todepress the plunger 22 and spring 23. When the sear engages the hammeras illustrated in FIG. 1, the sear extends generally in the positionshown in FIG. 7 in which the flat camming surface 43 extends angularlydownwardly with respect to the horizontal.

The kiln gun is shown in its ready to fire position in FIG. 1. Thehammer 19 has been engaged and cocked by the sear, the firing pin 18 isapproaching horizontal alignment with the shell, and the top surface 48of the operating arm 24 is just below the cam 42. As the lever arm 26 isrotated forwardly from the position shown in solid in FIG. 1, the topsurface of the operating arm will engage the camming surface 43 of thecam and cause the sear to rotate clockwise about the mounting pin 33.The relationship between the camming surface and the operating arm issuch that the sear will be rotated suffciently to release the hammerafter the firing pin is raised sufficiently to strike the shell properlybut before the operating arm reaches its upper limit of travel.

The kiln gun is shown in its fired position in FIG. 2. The operating armhas reached its fully raised position in which the upper surface thereofextends generally horizontally, the sear has been rotated clockwise torelease the hammer, and the spring-actuated plunger 22 has swung thehammer into engagement with the firing pin 18.

As can be best seen in FIG. 4, the operating arm engages the cam acrosssubstantially the full width of the operating arm, and this substantialarea of contact minimizes wear of these parts. Also, both the uppersurface of the operating arm and the camming surface are flat, and evenif the points of initial contact become worn, this will not affect thetimed release of the hammer. When the operating arm reaches its upperlimit of travel, the portion of the upper surface of the operating armwhich engages the camming surface and the camming surface aresubstantially in facing contact.

I have found it advantageous to provide the sear and cam from hardenedsteel to further minimize wear, and in one specific embodiment the searand cam were cast integrally from AISI 4330 steel and hardened to aRockwell hardness of from about 48 to about 52. I have also found itadvantageous to harden the operating arm, or at least the upper surfacethereof, and in one specific embodiment the operating arm was cyanidehardened to a file hard surface. This permits some initial adjustment ofthe relationship between the operating arm and the cam. If the operatingarm disengages the sear from the hammer prematurely, the upper surfaceof the operating arm can be filed away until the desired timedrelationship is established. This initial adjustment can be made at thefactory, and once it is made, no further adjustment is necessary ordesired. Accordingly, the firing mechanism has no parts which can bemisadjusted or tampered with by the user.

In one specific embodiment of the cam-equipped sear, the camming surface43 extended at an angle of about 15 from the horizontal, and the flatsurface 44 extended generally perpendicularly thereto. The cammingsurface was spaced about 0.240 inch from the center of the pivot opening46 along a line extending perpendicularly to the camming surface andthrough the center of the pivot opening, and the length of the cammingsurface from the front surface 44 to this perpendicular line was about0.275 inch. The tip of the cam at the juncture of the surface 43 and 44was therefore spaced about 0.268 inch vertically below the center of thepivot opening, and when the camming surface was rotated to a horizontalposition by the operating arm, the camming surface would be positionedabout 0.240 inch below the center of the opening, or about 0.028 inchabove its lowermost point position in the ready to fire position. Thelateral extent of the camming surface was about 0.605 inch, and thewidth of the operating arm was about 0.500 inch. The cam extendedlaterally above the operating arm for between one-half of the width ofthe arm to the full width thereof. The hammer-engaging surface of thetooth 40 was positioned about 0.705 inch from the center of the pivotopening, and the length of the hammer tooth 47 was about 0.10 inch, thelength of the sear tooth being somewhat greater.

While in the foregoing specification a detailed description of aspecific embodiment of the invention was set forth for the purpose ofillustration, it is to be understood that many of the details hereingiven may be varied considerably by those skilled in the art withoutdeparting from the spirit and scope of the invention.

We claim:

1. In a firearm having a yoke provided with a vertical breech blockpassage, a barrel attached to the yoke and having a shell-receivingchamber communicating with the breech block passage, an elongated breechblock vertically slidably received by the breech block passage, firingpin means carried by the breech block and movable between unfired andfired positions, the breech block being movable between an unfiredposition and a fired position in which the firing pin means isengageable with a shell received in the chamber, hammer means pivotallymounted in the breech block for movement between an unfired position anda fired position in which it engages the firing pin means, and springmeans carried by the breech block for biasing the hammer means into thefired position and into engagement with the firing pin means to move thefiring pin means from the unfired to the tired position, the improvedfiring mechanism comprising an elongated operating arm movably mountedon the firearm and extending adjacent the breech block, means connectingthe operating arm and the breech block for causing vertical slidingmovement of the breech block as the operating arm moves, a searpivotally mounted on the yoke for movement between unfired and firedpositions, the sear being engageable with the hammer means when both thesear and the hammer means are in the unfired position to hold the hammermeans against the bias of the spring means, and a cam carried by thesear engageable with the operating arm as the operating arm moves thebreech block to the fired position whereby the sear is pivoted torelease the hammer means.

2. The structure of claim 1 in which the firing pin means, the hammermeans and the sear are generally aligned for movement in a verticalplane through the breech block and the operating arm is movable in aplane generally parallel to said vertical plane and laterally offsettherefrom, the cam extending laterally from the sear above the operatingarm.

3. The structure of claim 2 in which the cam includes a substantiallyflat camming surface which extends at an acute angle from the horizontalwhen the sear is in the unfired position, the operating arm having asubstantially flat upper surface engageable with the camming surface,the fiat upper surface of the operating arm extending at an acute anglefrom the horizontal when it first engages the camming surface and boththe fiat upper surface and the camming surface extending generallyhorizontally when the sear is in the fired position.

4. The structure of claim 3 in which the camming surface extends at anangle of about 15 from the horizontal when the sear is in the unfiredposition.

5. The structure of claim 2 in which the cam includes a substantiallyflat camming surface which extends laterally from the sear above theoperating arm, the operating arm having a substantially flat uppersurface engageable with the camming surface for moving the sear from theunfired position to the fired position, the lateral extent of theengaging portions of the camming surface and the flat upper surface ofthe operating arm being at least about one-fourth inch.

6. The structure of claim 5 in which the camming surface and the flatupper surface of the operating arm are formed of hardened steel.

7. The structure of claim 6 in which the camming surface has a Rockwellhardness of about 48 to about 52.

8. The structure of claim 5 in which the sear and the cam are formedintegrally.

9. The structure of claim 5 in which the sear and the cam are formedintegrally by casting.

1. In a firearm having a yoke provided with a vertical breech blockpassage, a barrel attached to the yoke and having a shellreceivingchamber communicating with the breech block passage, an elongated breechblock vertically slidably received by the breech block passage, firingpin means carried by the breech block and movable between unfired andfired positions, the breech block being movable between an unfiredposition and a fired position in which the firing pin means isengageable with a shell received in the chamber, hammer means pivotallymounted in the breech block for movement between an unfired position anda fired position in which it engages the firing pin means, and springmeans carried by the breech block for biasing the hammer means into thefired position and into engagement with the firing pin means to move thefiring pin means from the unfired to the fired position, the improvedfiring mechanism comprising an elongated operating arm movably mountedon the firearm and extending adjacent the breech block, means connectingthe operating arm and the breech block for causing vertical slidingmovement of the breech block as the operating arm moves, a searpivotally mounted on the yoke for movement between unfired and firedpositions, the sear being engageable with the hammer means when both thesear and the hammer means are in the unfired position to hold the hammermeans against the bias of the spring means, and a cam carried by thesear engageable with the operating arm as the operating arm moves thebreech block to the fired position whereby the sear is pivoted torelease the hammer means.
 2. The structure of claim 1 in which thefiring pin means, the hammer means and the sear are generally alignedfor movement in a vertical plane through the breech block and theoperating arm is movable in a plane generally parallel to said verticalplane and laterally offset therefrom, the cam extending laterally fromthe sear above the operating arm.
 3. The structure of claim 2 in whichthe cam includes a substantially flat cammIng surface which extends atan acute angle from the horizontal when the sear is in the unfiredposition, the operating arm having a substantially flat upper surfaceengageable with the camming surface, the flat upper surface of theoperating arm extending at an acute angle from the horizontal when itfirst engages the camming surface and both the flat upper surface andthe camming surface extending generally horizontally when the sear is inthe fired position.
 4. The structure of claim 3 in which the cammingsurface extends at an angle of about 15* from the horizontal when thesear is in the unfired position.
 5. The structure of claim 2 in whichthe cam includes a substantially flat camming surface which extendslaterally from the sear above the operating arm, the operating armhaving a substantially flat upper surface engageable with the cammingsurface for moving the sear from the unfired position to the firedposition, the lateral extent of the engaging portions of the cammingsurface and the flat upper surface of the operating arm being at leastabout one-fourth inch.
 6. The structure of claim 5 in which the cammingsurface and the flat upper surface of the operating arm are formed ofhardened steel.
 7. The structure of claim 6 in which the camming surfacehas a Rockwell hardness of about 48 to about
 52. 8. The structure ofclaim 5 in which the sear and the cam are formed integrally.
 9. Thestructure of claim 5 in which the sear and the cam are formed integrallyby casting.